A tropical low in the Coral Sea off far north Queensland is a 25 per cent chance of becoming a cyclone by Thursday, the Bureau of Meteorology says.
It was only considered a 10 per cent chance just days ago.
Whether it develops into a cyclone or not, the system is set to bring yet more rain - and plenty of it.
"We haven't got our thumb yet on which is the most likely scenario, but in far north Queensland, it's raining anyway," the bureau's Livio Regano told AAP.
Mr Regano said a southeasterly airflow was interacting with a monsoon trough, dumping huge falls between Townsville and Cairns.
He said one possible model had the low, currently located east of Willis Island in the far north, tracking deep into the state's southeast corner, where rain and showers would be welcome.
Another has it moving west inland, where it could join forces with another low.
That would be bad news for graziers in the Gulf Country, with the Flinders and Cloncurry Rivers already in flood.
Huge falls are forecast for the Wet Tropics this week, with 286mm falling overnight at the Abergowrie Bridge near Ingham and major flooding also declared in the Herbert River.
Large areas of the outback are already underwater, with some remote Queensland communities expected to be isolated for weeks.
Flash flooding has affected much of inland Australia in recent days, claiming the life of a motorcyclist who tried to cross an inundated creek at Eurelia, in South Australia's Flinders Ranges, on Sunday morning.
In the Northern Territory, an emergency situation has been declared for parts of the Barkly and Central Australia regions, with two schools in Alice Springs closed on Monday to be used as shelters.
Southern states have not been spared, with residents of Mildura in Victoria's far northwest waking up to flash flooding after the town was soaked by 100mm of rain in 24 hours.
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